It's up to you buddy but I wouldn't go a penny over 6k, when I bought my 06 plate 2yrs ago the guy said he was sick of people ringing him and offering 5 or 5 and a half grand! I also offered a dealer 6k for a nice blue one he'd just had in and he gave me the "I will get 7 all day long speech", one week later he rang me back to see if we could do a deal.
Trust me dude 6k is enough to pay for a ten year old golf, if they want too much just walk away, they're out there...